1. Field of the Invention
The present invention relates generally to disk drive apparatus for recording and reproducing information on or from a floppy disk or the like, and more particularly, to improvements of heads and head seeking mechanisms used in disk drive apparatus.
2. Description of Related Art
The above-mentioned disk drive apparatus typically includes a magnetic head for recording and reproducing information, and a head seeking mechanism (carriage driving mechanism) for moving the head in the radial direction with respect to the disk. A known head seeking mechanism uses a rack and a pinion to move a carriage upon which a head is mounted. See, e.g., Japanese Laid-Open Patent Publication No. 276473/1989.
FIG. 24 is an exploded perspective view illustrating the carriage driving mechanism in this conventional disk drive apparatus. FIG. 25 is a vertical sectional view of FIG. 24.
As depicted in FIGS. 24 and 25, the conventional structure uses a pinion 502 provided on an output shaft of a step motor 501 to engage with a rack 504 provided on a carriage 503. The rack 504 is biased by a pre-load spring 505 in the direction of arrow u (toward pinion 502) of the figure, thereby giving a pre-load between the rack 504 and the pinion 502. Backlash which may occur between pinion 502 and rack 504 is thereby prevented. The carriage 503, upon which a head 506 is mounted, is accurately movement-positioned by rotation of the step motor 501.
Reaction against the pre-load applied between the rack 504 and the pinion 502 is received by a pulley 508 provided on the output shaft of the step motor 501. The carriage 503 is constructed so as to be slidable along a guide shaft 507.
As explained above, in the conventional device, if backlash is caused in the engagement of the rack 504 with the pinion 502, the rotation of the pinion 502 is not precisely transferred to the rack 504. Hence, the rack 504 is positively held against pinion 502 by the pre-load spring 505 so as not to cause backlash by giving the preload between the rack 504 and the pinion 502. The reaction thereof is received by the pulley 508. That is, pulley 508 prevents an excessive force from being applied by spring 505 to the drive shaft of motor 501 so that the drive shaft is not damaged.
Accordingly, the conventional carriage drive mechanism requires multiple members such as the pulley 508 and the spring 505 for providing a pre-load to the rack 504 and the pinion 502. This is a limiting factor in terms of miniaturizing and thinning of the disk drive apparatus. Further, the rack 504 and the carriage 503 can not be fixedly attached to each other in the above arrangement in order to apply the above-mentioned preload. It is required that the rack 504 be so constructed as to be movable relative to the carriage 503 (in the vertical direction in FIG. 1). However, the carriage 503 and rack 504 often become fixed to each other, leading to backlash, and therefore if employed for a long period of time, the positioning accuracy of the carriage 503 is deteriorated.